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A young girl skis at Alta Ski Area on a snowy day

Return of
La Niña

By Adam Fehr 10-13-2020

what exactly does a La Niña winter mean and what can we expect in Little Cottonwood Canyon?

This summer and fall have been abnormally warm and dry at Alta. While this weather is perfect for trail running and hiking, it’s around this time of year when we start to see the first significant snow accumulation in Little Cottonwood Canyon. Our extended Indian Summer was briefly interrupted with a little winter weather this past weekend. While we didn’t see a ton of accumulation—only 1.3” of snow at Alta—it appears that the weather is trending colder and slightly more active. A great reminder that winter is right around the corner.

Opening Day is tentatively scheduled for November 23rd, that’s less than 40 days away. While operations may look a little different this season due to the COVID-19 pandemic, we’re looking forward to the familiar sight of our mountains dressed in white.

All of the preseason weather discussions have focused on the return of a La Niña winter to North America. Fresh off their 50th birthday celebration, the good people at NOAA are calling for a 90% chance of La Niña conditions for a good chunk of the upcoming ski season.

So what exactly does a La Niña winter mean and what can we expect in Little Cottonwood Canyon?

While our snow, trees, mountains and sunshine are some of our most valuable resources at Alta Ski Area, not far down that list is our good friend Evan Thayer. Evan, a new father, is the skier behind Wasatch Snow Forecast and Open Snow’s Utah Daily Snow report. Evan is also a die-hard Alta powderhound. You can find him most powder mornings waiting for first chair on the Sunnyside lift.

Evan Thayer of Wasatch Snow Forecast

Evan Thayer of Wasatch Snow Forecast inspecting the Alta snow | Photo: Photo-John

For more information about La Niña and other long-range forecasting takeaways, or lack thereof, here’s a little Q&A with Evan Thayer, the Pow Slayer.

Other than Spanish for little girl, what is La Niña?

Evan: La Niña is the opposite of El Niño. That means that rather than warmer-than-normal sea surface temperatures in a certain area of the Central Pacific, we see cooler water temperatures. Both El Niño and La Niña can have significant impacts on the weather patterns in North America and around the world.

How does La Niña effect snowfall in North America?

Evan: La Niña often leads to an enhanced strength of the northern branch of the jet stream. The jet stream is the current of atmospheric winds that carry storms across the continent, generally from west to east. The jet stream has a tendency to split into northern and southern branches. In a La Niña winter, the northern branch tends to be stronger. This often means that areas farther north receive more precipitation.

Are we looking at a weak, moderate or strong La Niña?

Evan: So far, this is looking to be a weak-to-moderate strength La Niña. That means the temperatures in this key region of the Pacific Ocean that drives La Niña/El Nino are about 0.5 to 1.0℃ below normal. In general, this means the typical impacts of La Niña on the atmosphere should be noticeable, but not as extreme as a strong event.

What does that mean for Utah?

Evan: Utah is a mid-latitude state, so it is neither particularly far north, nor south in the country or continent. That means that the impacts of La Niña, like El Nino, are not particularly strong. We are also located well inland, away from the coast where the differential in above and below normal precipitation is more pronounced. In short, we have seen both very good winters, and very poor winters during La Niña.

What does that mean for Alta?

Evan: Alta is located in the central portion of the Wasatch Mountain range. The Wasatch mountains are generally located in the northern half of Utah. That means that Alta is firmly located in the Northern half of the state. In theory, this would mean that Alta would be slightly more likely to benefit from the strong northern branch of the jet stream.

Unfortunately, La Niña does not guarantee a well-above-average winter anywhere, especially in Utah. At best, we are only slightly stacking the deck in our favor. However, you can take solace knowing that when you average over 500” of annual snowfall, every season is going to be awesome, it’s just a matter of what degree of awesome it will be.

...when you average over 500” of annual snowfall, every season is going to be awesome, it’s just a matter of what degree of awesome it will be.

Let’s take a look at similar La Niña winters, compare that to Alta's 540" of average seasonal snowfall and what we can expect, or not, for 2020-21.

La Niña winters and seasonal Snowfall totals at Alta since 1980:

  • 1983-84 = 708.5” | 3rd most
  • 1984-85 = 426.5”
  • 1988-89 = 581”
  • 1995-96 = 543.5”
  • 1998-99 = 521.5”
  • 1999-00 = 508.5”
  • 2000-01 = 549”
  • 2005-06 = 641.5”
  • 2007-08 = 702”
  • 2008-09 = 696”
  • 2010-11 = 724” | 2nd most
  • 2011-12 = 390.5” | 5th least
  • 2016-17 = 596.5”
  • 2017-18 = 388” | 4th least

El análisis:

  • 14 La Niña events since 1980
  • 8 winters with above-average snowfall
  • 6 winters with below-average snowfall
  • 570” average on La Niña Years = 4% above average

The odds have us at a 90% chance of a La Niña for the better part of the 2020-21 ski season. Historically, 57% of La Niña winters have seen above-average snowfall with an average of 570” of snow.

The Town of Alta welcome sign buried by snow

The Town of Alta welcome sign buried by snow | Photo: Rocko Menzyk

While we have seen some great La Niña winters at Alta, we have also seen some duds. There's no way of predicting how a La Niña winter will affect our snowfall at Alta. Luckily, Alta has averaged 540" of snow every year since 1980. While other ski areas in North America see significant swings in La Niña or El Niño winters, Alta has experienced an average snowfall range between 95-104% of normal. Even the worst and best years in the past 40 have fallen in the 70-130% range.

Looking at long-range forecast models can be fun, but it's far from an exact science. The good news is that nothing in the long-range forecast predicts anything that we haven't seen before at Alta. La Niña? El Niño? ENSO neutral? We've weathered every type of winter since 1938.

Without further ado, our best-guess forecast for the winter of 2020-21:

It will snow at Alta and we will ski it. There will be stormy days, bluebird days, greybird days and sleeper days. There will be periods of high pressure, low pressure and no pressure. At some point, you will hear someone claim to have had their "best day ever." After an eight-month offseason, with all that's going on in the real world, we're just excited to ride some lifts and slide down a mountain again soon.

Wildcat lift at Alta Ski Area | Photo: Iz La Motte

Wildcat lift at Alta Ski Area | Photo: Iz La Motte

Stay safe. Stay healthy. Stay skiing.

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